There has been proposed a related art communication unit for conducting data communications and a telephone call using a predetermined frequency band. The related art communication unit uses the same frequency band for data communications and a telephone call. For example, a wireless Local Area Network (LAN) intended for data communications and a digital codeless telephone (DCL) intended for a telephone call use the same frequency band of 2.4 GHz.
The frequency band and frequency channels used with the wireless LAN and the DCL will be discussed with reference to FIG. 10. FIG. 10 is a schematic drawing to show the frequency band and frequency channels used with the wireless LAN and the DCL.
As shown in FIG. 10, each of the communication systems of the wireless LAN and the DCL uses the communication band of 2.4 GHz to 2.5 GHz (2.4 GHz band). Channels into which the frequency band is divided are set corresponding to the communication systems of the wireless LAN and the DCL. To distinguish the channels in the communication system of the wireless LAN from those in the communication system of the DCL, hereinafter the channels used with the wireless LAN will be referred to as wireless LAN channels and the channels used with the DCL will be referred to as DCL channels.
In the wireless LAN, the communication band of 2.4 GHz to 2.5 GHz is divided into 14 wireless LAN channels (wch1 to wch14). In the wireless LAN, one of the 14 wireless LAN channels is used continuously.
In the DCL, the communication band of 2.4 GHz to 2.5 GHz is divided into 89 DCL channels (dch1 to dch89). For each predetermined period called hopping period (for example, 1/100 seconds), the DCL channel to be used is changed among the preselected, for example, 45 DCL channels of the 89 DCL channels (hopping).